1F40
1F00
1EC0
1E80
1E40
1E00
1DC0
1D80
1D40
1D00
1CC0
1C80
1C40
1C00
1BC0
1B80
1B40
1B3F
EP0IN
EP0OUT
EP1IN
EP1OUT
EP2IN
EP2OUT
EP3IN
EP3OUT
EP4IN
EP4OUT
EP5IN
EP5OUT
EP6IN
EP06UT
EP7IN
EP07OUT
Code/Data
RAM
0000
Figure 3-3. Unused Bulk Endpoint Buffers (Shaded) Used as Data Memory
In the example shown in Figure 3-3, only endpoints 0-IN through 3-IN are used for the
USB function, so the data RAM (shaded) can be extended to 0x1D7F.
If an application uses none of the 16 EZ-USB isochronous endpoints, the 8051 can set the
ISODISAB bit in the ISOCTL register to disable all 16 isochronous endpoints, and make
the 2-KB of isochronous FIFO RAM available as 8051 data RAM at 0x2000-0x27FF.
Setting ISODISAB=1 is an all or nothing choice, as all 16 isochronous endpoints are dis-
abled. An application that sets this bit must never attempt to transfer data over an isochro-
nous endpoint.
The memory map figures in the remainder of this chapter assume that ISODISAB=0, the
default (and normal) case.
EZ-USB TRM v1.9
Chapter 3. EZ-USB Memory
Page 3-3
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